#include <cstdio>
#include <iostream>
#include <string>

std::string sayHello() 
{
#ifdef IS_WINDOWS
    return "Hello World from Windows";
#elif defined(IS_LINUX)
    return "Hello World from Linux";
#elif defined(IS_MACOS)
    return "Hello World from MacOS";
#else
    return "Hello World from Unknown";
#endif

}

int main(int argc, char** argv)
{
    std::cout << sayHello() << std::endl;
    return EXIT_SUCCESS;
}
